The best advice is to download the latest data sheet for your PIC, grab a highlighter, check what features are available.
Then check the appropriate section, and change the registers as needed.
For example, your 18F4550 has a potential 13 ADC Ports.
If you look on pg 262, of the current data sheet, ADCON1 = $F '(%00001111) setting will turn all your ADC ports into Digital.
Unfortunately I don't know of any list that will clearly show all available.
If you are having difficulties, post your code, and someone can point you in the right direciton.





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